This is an early reference to the idea of a non-interference directive, or as it is called in the Star Trek universe, the Prime Directive.

The ship leveled off. Steffens had no idea what to do; the sudden sight of the moving things had unnerved him. He had already sounded the alert, flicked out the defense screens. Now he had nothing to do. He tried to concentrate on what the League Law would have him do.

The Law was no help. Contact with planet-bound races was forbidden under any circumstances. But could a bunch of robots be called a race? The Law said nothing about robots because Earthmen had none...

The Mapping Command, they called it. Theoretically, all he was supposed to do was make a closeup examination of unexplored systems, checking for the presence of life-forms as well as for the possibilities of human colonization. Make a check and nothing else. But he knew very clearly that if he returned to Sirius base without investigating this robot situation, he could very well be court-martialed one way or the other, either for breaking the Law of Contact or for dereliction of duty.

Compare to the law on Relations with Extraterrestrial Life from Ogre (1944) by Clifford Simak, which provides an earlier reference. See also the entry for Prime Directive from With Folded Hands (1947) by Jack Williamson, although Williamson's (first use!) phrase does not quite have the modern meaning.